This invention relates to new triazine compounds which are useful as antiozonants for rubber, processes for their manufacture, and to their use in inhibiting the deteriorating effect of ozone on unsaturated polymers.
It is well known that ozone causes surface cracking of conventional highly unsaturated rubber vulcanizates when the rubber is placed under strain in an ozone environment. The most severe deterioration occurs when a small number of cracks are formed which grow rapidly into deep, disruptive fissures. These ozone cracks seriously shorten the serviceable life of the article.
Chemical antiozonants have been developed which retard the formation of the ozone cracks occurring under static and dynamic conditions. Examples of antiozonants in common use include: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine; N-phenyl-N'-isopropyl-p-phenylenediamine; N-phenyl-N'-(1,4-dimethylpentyl)-p-phenylenediamine; N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine: N-phenyl-N'-cyclohexyl-p-phenylenediamine: mixed diaryl-p-phenylenediamines: N,N'-diphenyl-p-phenylenediamine; N,N'-di-beta-naphthyl-p-phenylenediamine; N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine: N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine: N,N'-bis(1-methylheptyl)-p-phenylenediamine; N-phenyl-N'-p-toluenesulfonyl-p-phenylenediamine and blends of these materials.
The use of these well known paraphenylenediamine materials has improved ozone protection under both static and dynamic conditions, however, even the best of the class just described have a very strong tendency to both stain and discolor. The term "stain" or "staining" is herein used to describe the characteristic of a material to diffuse through a polymeric substrate and discolor the adjacent surface. This diffusion staining is highly objectionable in most light colored rubber articles. In tires, which is the largest application in which the ozone protection is required, the tendency to diffusion staining of the aforementioned paraphenylenediamine materials is objectionable particularly in white sidewall type tires. Even in non-white sidewall type tires, the tendency of the materials to diffuse to the surface of the tire sidewall can be objectionable in that a brown, dull surface is created on the tire sidewall. This is aesthetically objectionable in that it detracts from the general jet black, smooth appearance of a new tire. It is obvious that in a white sidewall tire, the migration of the brown discoloring material to the surface of the white sidewall is highly objectionable and generally difficult to remove during cleaning of the tire surface.
Waxes have been long utilized to inhibit ozone cracking in articles under stress in static condition by incorporating the wax into the rubber compound prior to vulcanization. The wax functions by migrating to the surface of the rubber article to form a film which acts as a physical barrier to the ozone attack. However, during dynamic flexing in service, the wax film is cracked or disrupted and the tendency is for the article to exhibit fewer and more severe ozone cracks than if no wax had been incorporated. Therefore, for many service conditions, the use of wax is impractical due to the dynamic conditions under which the article is expected to perform.
An object of this invention is to provide an antiozonant material which is highly effective in protecting a highly unsaturated polymer substrate from ozone attack. A further object is to provide ozone protection in a static condition at very low levels and to protect the rubber article during extended aging conditions against ozone attack. Yet another object is to produce a compound which does slowly diffuse and does not produce an objectionable brown bloom.
The novel substituted triazine compounds of the invention have provided exceptional long term ozone protection under static conditions with and without using wax. An advantage of the substituted triazine compounds is that it produces a substantially non-staining antiozonant of high molecular weight. A further advantage is that it slowly blooms to the surface of the rubber article. A further advantage is that the triazine compounds of the invention provide outstanding dynamic protection without the use of waxes preferably by blending said triazine compounds with other known antiozonants and antioxidants. Another advantage is that the compounds do not tend to increase scorchiness of the compounded rubber stock in which it is used. This improves processing safety over other paraphenylenediamine antiozonants.